This invention relates in general to interface circuits in Open Telecom Platform (OTP) communication systems, and more particularly to a detector in an interface circuit for signaling the occurrence of unexpected asynchronous events within the system to a predetermined destination address using structured messages.
Many modem CODECs (Coder-Decoders) and trunk interface circuits provide line status information in a serial format. Traditionally, the detection of asynchronous events, such as a line going off-hook, has been accomplished by means of microprocessor polling or sampling of predetermined line status bits to detect logic level changes. This has required either the use of a dedicated microprocessor at each node which is capable of indicating a status change, or the provision of a mechanism by which all status information is switched through the system to a central microprocessor. Both of these prior art approaches require dedicated system resources, either in the form of local microprocessors or additional switching circuits.
According to the present invention, an event detector is integrated into a Peripheral Interface Application Specific Integrated Circuit (PASIC) which is used as an interface between serial data streams in an OTP switching system. According to the preferred embodiment, the PASIC device which incorporates the event detector, is used as an interface between a plurality of serial links configured according to the Mitel(copyright) ST-BUS standard and a further plurality of serial links configured according to the H.100 of generic high-bandwidth TDM (Time Division Multiplex) bus and control, issued by the ECTF (Enterprise Computer Telephony Forumxe2x80x94a telecommunications standards agency). Thus, the event detector of the present invention requires no additional system resources since it is incorporated within an existing piece of hardware within the OTP system.
The event detector of the present invention detects a plurality of different possible asynchronous events (up to 256 events in the preferred embodiment) from any of a plurality of source addresses and nodes, debounces the event and, once a valid event has been identified and confirmed, formats and transmits a message via a message transport system to a predetermined destination address for further appropriate action. According to the preferred embodiment, each event is time-stamped so that latency in the message transport system does not affect time-critical events. Thus, the transmitted message identifies the source address, source node, an event number for identifying the event, and a time-stamp associated with the event.